This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
It will come as no surprise that software distributors are facing piracy in the sense that some people are using unauthorized copies of the software applications without paying for them. This is particularly true in the domain of computer games. Game providers and distributors therefore use protection mechanisms and in an attempt to thwart such piracy. Such protection mechanisms include:                SecuROM        SafeMedia        Changing address marks and other marks or sync fields on floppy disks.        The use of data on CD-ROMs in places where it cannot be written on a CD-R.        Having the software require evidence of purchase to work properly. Registration keys and serial numbers may also be used this way.        Dongles        Bus encryption        A keyfile that must be stored in the same directory as the software execution file.        Product activation via phone or the Internet.        
The software is often tied to a certain computer through a unique identifier of the computer, such as a hardware serial number or MAC address, but this is difficult on a standard PC as only few such identifiers are easily available. Furthermore, if the identifier is set in a file (such as a keyfile), then the file itself may be copied to another computer, and the MAC address may be changed on modern Ethernet cards, thus overcoming the copy protection.
In addition to the problems already mentioned, hackers often react by developing tools that at least partly defeat these protection mechanisms.
Banikazemi et al. present an intrusion detection system (IDS) in “Storage-base File System Integrity Checker”. The system is able to detect modifications to data and also allows a roll-back to unmodified versions of the data. The IDS comprises a number of hosts that store data on centralised disks, and a distinct Storage Area Networks Volume Controller (SVC). The SVC generates verification data by, among other things, reading metadata such as superblock and inode tables for theliles. The verification data is then stored in a location that is inaccessible by the hosts, in order to ascertain that these do not tamper with the verification data. The SVC then uses for instance the inode numbers to verify if an intrusion has modified the files. While the system may work well for intrusion detection, it does not prevent copying of files.
It can therefore be appreciated that there is a need for a further copy protection scheme, in particular one that may work on a standard PC. The present invention provides such a solution.